This application is based upon and claims the benefit of priority from the prior Japanese Patent Applications No. 2000-330534, filed Oct. 30, 2000, and No. 2000-390987, filed Dec. 22, 2000, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to an X-ray diagnosis apparatus including a mechanism capable of supporting an X-ray tube and an imaging system in arbitrary positions so that the imaging direction can be freely changed.
2. Description of the Related Art
In X-ray diagnoses, particularly in angiography of an object to be examined, a mechanism for holding, e.g., a C- or U-shaped arm is used. An X-ray tube and an imaging system are attached to this C-arm. The imaging system is composed of an image intensifier, optical system, and TV camera.
The C-arm is supported by the support mechanism so as to be rotatable around three perpendicular axes crossing one another and to be slidable along two perpendicular axes. Accordingly, an object to be examined can be imaged from an arbitrary position in an arbitrary direction.
In advancing a catheter to a morbid portion of a blood vessel under fluoroscopy of an angiographic image, an operator can better understand the blood vessel in which the catheter is to be advanced if the blood vessel is separated from other blood vessels around it. However, when the configuration (blood vessel structure) of blood vessels is complicated as in the case of cerebral blood vessels, a blood vessel in which a catheter is to be advanced overlaps other blood vessels without being separated from them. This often makes an operator unable to well understand the blood vessel of interest.
Accordingly, to find an imaging direction along which blood vessels overlap little and an operator can better understand a blood vessel in which a catheter is to be advanced, angiography must be performed several times by changing the imaging position and imaging direction. Unfortunately, this cannot be performed in reality because a large amount of contrast agent must be injected into an object to be examined to cause side effects and the object undergoes a large amount of X-ray exposure. Therefore, an operator must manually perform operation with a blood vessel in which a catheter is to be advanced not separated from other blood vessels.
In this case, it is very difficult for the operator to advance the catheter to a morbid portion to be cured, resulting in a prolonged examination time and operation time. This increases the burdens on the patient and on the operator.
The following problem also arises. In a certain conventional imaging method, the contrast of a blood vessel is emphasized by injecting a contrast agent into an object to be examined. An X-ray diagnosis apparatus suited to this imaging method is generally called an xe2x80x9cangiographic apparatusxe2x80x9d. This angiographic apparatus allows the insertion of a catheter into an object to be examined under X-ray fluoroscopy. In addition, imaging (so-called xe2x80x9cbolus chasexe2x80x9d imaging) which chases the flow of a contrast agent can be performed by moving the C-arm during the imaging.
In this X-ray diagnosis apparatus, the work of setting the C-arm in a position optimum for an interest portion (e.g., a morbid portion) inside an object to be examined is important. Conventionally, an operator always performs this work while monitoring a fluoroscopic image. Since, however, a fluoroscopic image is used to determine the imaging position, an object to be examined is continuously exposed to X-rays while the bed and the C-prm are moved and positioned. That is, the work of positioning increases the exposure dose of an object to be examined.
This problem is particularly serious in multi-direction X-ray imaging. That is, this multi-direction X-ray imaging requires the positioning work as described above in each and every direction in principle, so the exposure dose of an object to be examined increases accordingly.
To eliminate this abuse, positioning is sometimes performed in accordance with the memorized results of fluoroscopy performed within short time periods. However, confirmation using a fluoroscopic image is again necessary. This decreases the exposure dose xe2x80x9creducingxe2x80x9d effect. It is well possible that no satisfactory result is obtained by one-time positioning. As a consequence, X-ray fluoroscopy, stop of the fluoroscopy, and positioning are sometimes repeatedly performed. In a case, not only the inspection time is prolonged but also the exposure dose is increased instead of being reduced.
This problem applies to the setting of so-called X-ray irradiation conditions. The X-ray irradiation conditions include the tube voltage and tube current (filament current) of an X-ray tube, the irradiation time, and the like. These X-ray irradiation conditions are set for each inspection in accordance with the physical constitution of an object to be examined and with a portion to be imaged. Similar to the positioning, the X-ray irradiation conditions are determined under X-ray fluoroscopy.
It is an object of the present invention to shorten the time required for positioning and reduce the exposure dose in an X-ray diagnosis apparatus.
According to an aspect of the present invention, an X-ray diagnosis apparatus comprises an X-ray tube, an imaging system which detects X-rays emitted from the X-ray tube and transmitted through an object to be examined and generates X-ray image data, an arm which supports the X-ray tube and the imaging system, an arm support mechanism which rotatably and movably supports the arm, and a bed which holds the object between the X-ray tube and the imaging system. This X-ray diagnosis apparatus further comprises a three-dimensional image generating unit which generates three-dimensional image data from volume data concerning the object, a display unit which displays the three-dimensional image data, an input device which designates an interest point on the displayed three-dimensional image data, and a controller which controls at least one of the arm support mechanism and the bed, such that the center of the X-ray image data generated by the imaging system is positioned on a portion of the object which substantially corresponds to the designated interest point.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.